In order for gene therapy of the hemoglobinopathies to become a reality, gene transfer must be developed that are capable of high-level expression, that can efficiently transduce hematopoietic stem cells, and do not cause disease. The goal of this project is to perform studies relevant to these three challenges. Specific Aim 1 is directed toward our continued investigations of chromatin insulators, elements that can increase both the expression and possibly the safety of gene transfer vectors. This includes testing the activity of a prototypic insulator in a primate transplantation model, and cloning and characterizing new chromatin insulators. Specific Aim 2 is directed toward characterizing new chromatin insulators. Specific Aim 2 is directed toward characterizing the sites of vector integration in clinically, relevant hematopoietic cells, with a special emphasis on identifying any preference for open chromatin, a unique chromosomal structure associated with active genes. Specific Aim 3 is directed toward characterizing the properties of virus vectors for globin gene available now and to be developed by the Program Project participants, in a clinically relevant primate transplantation model. This includes vectors base on a variety of recombinant viruses such as oncoretroviruses, lentiviruses, foamy viruses, and hybrid adeno / adeno-associated viruses. Combined with the other Projects of this Program Project, these specific aims will improve both the safety and efficacy of recombinant virus vectors for globin genes, and provide critical insights into the potential risks and benefits of these vectors prior to their use in clinical trials.